[newlib-cygwin] Cygwin: Fix cygheap corruption caused by cloned atomic buffer

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=af85fdd73f6ac87e02ee2872e415e7e89d7111f4

commit af85fdd73f6ac87e02ee2872e415e7e89d7111f4
Author: David McFarland <corngood@gmail.com>
Date:   Sun Oct 28 16:22:44 2018 -0300

    Cygwin: Fix cygheap corruption caused by cloned atomic buffer
    
    The fhandler_base_overlapped::copyto clears atomic_write_buf on the
    clone, but none of the derived classes were doing this.  This allowed
    the destructor to double-free the buffer and corrupt cygheap.
    Clear atomic_write_buf in copyto of all derived classes.

Diff:
---
 winsup/cygwin/fhandler.h     | 2 ++
 winsup/cygwin/release/2.11.2 | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 2cc99d7..9e63867 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1216,6 +1216,7 @@ public:
   {
     x->pc.free_strings ();
     *reinterpret_cast<fhandler_pipe *> (x) = *this;
+    reinterpret_cast<fhandler_pipe *> (x)->atomic_write_buf = NULL;
     x->reset (this);
   }
 
@@ -1256,6 +1257,7 @@ public:
   {
     x->pc.free_strings ();
     *reinterpret_cast<fhandler_fifo *> (x) = *this;
+    reinterpret_cast<fhandler_fifo *> (x)->atomic_write_buf = NULL;
     x->reset (this);
   }
 
diff --git a/winsup/cygwin/release/2.11.2 b/winsup/cygwin/release/2.11.2
index c8d81d4..b9ccc5c 100644
--- a/winsup/cygwin/release/2.11.2
+++ b/winsup/cygwin/release/2.11.2
@@ -11,3 +11,6 @@ Bug Fixes
 
 - Return ESPIPE rather than EINVAL from lseek on a fifo.
   Addresses: https://cygwin.com/ml/cygwin/2018-10/msg00019.html
+
+- Fix a memory corruption when using pipes or FIFOs
+  Addresses: https://cygwin.com/ml/cygwin-patches/2018-q4/msg00000.html